Trying to retrieve username from the database jquery

[GoReLe]

\[code\] echo "<form method='post' action='regprocess.php' id='registerform'>"; echo '<fieldset class="register">'; echo"<h2>Register</h2>"; echo "<ul>"; echo '<li><label for="FirstName">First Name: </label> <input type="text" name="FirstName" id="FirstName"></li>'; echo '<li><label for="LastName">Last Name: </label> <input type="text" name="LastName" id="LastName"></li>'; echo '<li><label for="Email">Email: </label><input type="email" name="Email" id="Email"></li>'; echo '<li><label for="Username">Username: </label><input type="text" name="Username" id="Username"></li>'; echo '<li><input type="button" id="check_username_availability" value="http://stackoverflow.com/questions/12764384/Check Availability"></li>'; echo '<div id="username_availability_result"></div>'; echo '<li><label for="Password">Password: </label><input type="password" name="Password" id="Password"></li>'; echo '<li><input type="submit" value="http://stackoverflow.com/questions/12764384/Register"></li>'; echo "</ul>"; echo "</fieldset>"; echo "</form>";<script src="http://stackoverflow.com//ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js"></script><SCRIPT LANGUAGE="JAVASCRIPT" TYPE="TEXT/JAVASCRIPT">$(document).ready(function() { var checking_html = 'Checking...'; //when button is clicked $('#check_username_availability').click(function(){ //run the character number check $('#username_availability_result').html(checking_html); check_availability(); }); }); //function to check username availability function check_availability(){ //get the username var username = $('#username').val(); //use ajax to run the check $.post("check_username.php", { username: username }, function(result){ //if the result is 1 if(result == 1){ //show that the username is available $('#username_availability_result').html(username + ' is Available'); }else{ //show that the username is NOT available $('#username_availability_result').html(username + ' is not Available'); } }); }</script><?php$conn = new mysqli('sapphire', 'cgreenheld', '', 'cgreenheld_dev');$username = mysqli_real_escape_string($conn, $_POST['Username']); //mysql query to select field username if it's equal to the username that we check ' $usernameresult = 'Select Username from User where Username = "'. $username .'"'; $uresult = $conn->query($usernameresult); //if number of rows fields is bigger them 0 that means it's NOT available ' if($uresult->num_rows==1) { //and we send 0 to the ajax request echo 0; }else{ //else if it's not bigger then 0, then it's available ' //and we send 1 to the ajax request echo 1; } ?>\[/code\]Hi everyone, I'm trying to check if a username is in the database, and I'm not sure quite what's wrong with my code, when it retrieves the stuff from the database it just always shows "undefined is not avaliable" so for some reason it's not retrieving the username, wondering if anyone could help me? I'm really stuck.. The php is in a different file just for anyone who wanted to know.